Pixelmon Mod

I was wondering how to put pokemon icons separately in a crate because if i use the pokepicture id it always turns into my most recent picture As you can see in the picture I want the squirtle to be a mewtwo but it turns back to mewtwo because the id defaults to the most recent picture is there any way to make the mewtwo icon stay as mewtwo? this is a crate that everyone will see and spin but I cannot figure this out...